The present invention relates to an image formation apparatus having a tuck prevention mechanism and, more particularly to an image formation apparatus having an improved tuck prevention control mechanism that prevents a tuck of a transfer material to an image holding body.
The present invention relates to an image formation apparatus, such as a laser beam printer using an electrostatographic method, having a tuck prevention control mechanism that prevents a tuck state on an image holding body to a transfer material and, more particularly to an image formation apparatus having an improved tuck prevention control mechanism that prevents an occurrence of a tuck state on a photosensitive body drum to a cut paper.
One kind of a conventional image formation apparatus structure is shown in FIG. 21, such an image formation apparatus is disclosed in Japanese Patent Laid-Open No. 172369/1982. In FIG. 21, the image formation apparatus mainly comprises a photosensitive body drum 1, an electrostatic charger 102, an exposure device 103, a development device 104, a transfer electrostatic charger 105, an erase lamp 106, a cleaner 107, a belt cleaner 108, a transfer material 109, a transfer material transportation belt 100, rollers 111, 112 and 113, a preliminary electrostatic charger 114, a ground roller 115 and an electrostatic discharger 116.
The above stated conventional image formation apparatus structure carries out the following motions. First of all, electric charging is given uniformly on a surface of the photosensitive body drum 1 by the electrostatic charger 102. After that, the light corresponding to the image to be formed is irradiated on the surface of the photosensitive body drum 101 from the exposure device 103 and the electrostatic latent image is formed on the surface of the photosensitive body drum 101.
The development device 104 stores an image formation medium (e.g., toners) In its interior portion. Those toners are given constant charge values in accordance with the triboelectric charging characteristic. Those toners are adhered on the surface of the photosensitive body drum 1 by the electrostatic force according to the above stated electrostatic latent image and then the visual image is formed on the surface of the photosensitive body drum 1.
The transfer material 109, such as a cut paper, is supplied into the image formation apparatus from a direction A as shown in FIG. 21. The transfer material 109 is loaded on the transfer material transportation belt 100 and transported by this transfer material transportation belt 100.
In this conventional image formation apparatus, since the transfer material transportation belt 100 and the transfer material 109 are adhered by the electric charging having the reversal polarity characteristic by the preliminary electrostatic charger 114 and the ground roller 115, the transfer material 109 is transported under the condition in which the transfer material 109 is absorbed by the transfer material transportation belt 100.
In a nip region in which the photosensitive body drum 1 and the transfer material transportation belt 100 make contact, since by the transfer electrostatic charger 105 the transfer material transportation belt 100 is given the reversal polarity electric charging against the polarity of the electric charging of the image formation medium (the toners), the toners on the photosensitive body drum 101 are transferred to the nip region. The transfer material 109 onto which surface the visual image has been transferred, is removed by the electric charging by the electrostatic discharger 116 in which the high alternative current is supplied.
After the transfer material 109 is separated at a portion of the roller 112 from the transfer material transportation belt 100, the transfer material 109 is transported toward a direction B as shown in FIG. 21. By fusing the toners according to a fixing element (not shown), the image is fixed on the surface of the transfer material 109.
During this process, the residual electric charging on the surface of the photosensitive body drum 101 is discharged with electric charge by the erase lamp 106 and the residual toners are removed by the cleaner 107 and the image formation apparatus then waits for next image formation. The scattered toners on the transfer material transportation belt 100 are removed by the belt cleaner 108.
FIG. 22 shows another conventional image formation apparatus structure having a drum tuck prevention element. In FIG. 22, the image formation apparatus has a claw 117 for peeling off the transfer material 109. The residual construction elements excluding the peel-off craw 117 in this image formation apparatus shown in FIG. 22 are same those construction elements in the image formation apparatus shown in FIG. 21. Generally, the reference number of the elements shown in FIG. 22 are the same as the corresponding elements shown in FIG. 21.
The image formation motions of this conventional image formation apparatus having the drum tuck prevention element shown in FIG. 22 are basically the same as those of the image formation apparatus shown in FIG. 21.
In this latter conventional image formation apparatus shown in FIG. 22, when wrapping by the transfer material 109 (the drum tuck phenomenon) occurs, in other words when the transfer material 109 is wrapped on the photosensitive body drum 101 according to some cause, the transfer material 109 is subsequently peeled off by the peel-off claw 117 which is in contact with o is disposed near the photosensitive body drum 1. Accordingly, comparing this device with the former image formation apparatus the occurrence of the drum tuck can be prevented in this later image formation apparatus.
In the former conventional image formation apparatus shown in FIG. 21, the occurrence of drum tuck or the tucking of the transfer material 109 to the photosensitive body drum 101 may be lowered with an electrostatic state, for example by increasing the electric charging amount of the preliminary electrostatic charger 114. However, the complete prevention of the occurrence of drum tuck is insufficient. Accordingly, at all times this former conventional image formation apparatus gives cause for anxiety about the drum tuck.
Even in the latter conventional image formation apparatus, where the drum tuck prevention element, the peel-off claw 117 provided to contact to or is disposed near the photosensitive body drum 101 to peel the transfer material from the photosensitive body drum 101, there are inconveniences. Namely, when the transfer material 109 is peeled off from the photosensitive body drum 101, the drum tuck prevention element disturbs the image on the photosensitive body drum 101 or due to contact with the peel-off claw 117 the photosensitive body drum 101 is damaged and this deteriorates the image during the after transfer process.
Further, even in the later image formation apparatus having the drum tuck prevention means, the degree to which the goal of preventing the drum tuck operation is achieved differs with each image formation apparatus according to the use frequency and the age and deterioration etc. In the image formation apparatus there is an inconvenience that the service man must to go to inspect regularly the image formation apparatus regardless of the success of the drum tuck prevention means operation.